(1) Field of the Invention
The present invention relates to a solenoid valve device which functions as one of intake valves and exhaust valves of an internal combustion engine.
(2) Description of the Related Art
As disclosed in Japanese Laid-Open Utility Model Application No.60-175805 and Japanese Laid-Open Patent Application No.6-129219, there is known a solenoid valve device which functions as one of intake valves and exhaust valves of an internal combustion engine. Such a solenoid valve device is provided with a valving element which opens and closes a fluid passage between a port and a combustion chamber of the engine by exerting an electromagnetic force between an armature and a core.
In the conventional solenoid valve device of the above publications, the armature is integrally formed with the valving element, and the armature and the valving element are supported so as to be movable in an axial direction of the device. A coil contained in the core is provided above the armature. As an exciting current is supplied to the coil, the electromagnetic force is exerted between the armature and the core. The valving element moves up and down in the axial direction in accordance with the movement of the armature relative to the core. Hence, in the conventional solenoid valve device, the valving element is actuated to open or close the fluid passage by supplying the exciting current to the coil or cutting the exciting current supplied to the coil.
The valving element moves to a valve-closed position and abuts on a valve seat at which the fluid passage is fully closed. At this time, the armature impacts on the core and an impact sound is produced. The higher the speed of movement of the armature when the valving element reaches the valve-closed position, the louder the impact sound due to the impact between the armature and the core.
In order to reduce the impact sound of the conventional solenoid valve device, it is desirable to reduce the speed of movement of the armature before the valving element reaches the valve-closed position. The conventional solenoid valve device of the above publications includes an impact absorbing spring provided at the top of the valving element opposite to the valve seat. The impact absorbing spring functions to reduce the speed of movement of the armature before the valving element reaches the valve-closed position. The impact absorbing spring exerts an actuating force on the armature and the valving element in a direction to push the valving element toward a valve-open position when the valving element is moving to the valve-closed position. By using the impact absorbing spring, the speed of movement of the armature before the valving element reaches the valve-closed position is reduced, and it is possible for the conventional solenoid valve device to reduce the impact sound.
However, in the conventional solenoid valve device of the above publications, the actuating force of the impact absorbing spring functions to push the valving element toward the valve-open position (or in the direction opposite to the valve-closed position) not only when the valving element moves to the valve-closed position but also when the valving element is held at the valve-closed position. It is required for the conventional solenoid valve device to supply a large amount of the exciting current to the coil when the valving element is held at the valve-closed position against the actuating force of the impact absorbing spring. The electromagnetic force which is greater than the actuating force of the impact absorbing spring must be produced by supplying the large amount of the exciting current in order to hold the valving element at the valve-closed position. Hence, it is difficult for the conventional solenoid valve device of the above publications to effectively decrease power consumption.